Fetal Vertebral Artery Doppler Reference Values at 19–41 Weeks of Gestation

Abstract

Objectives: To establish Doppler reference values for the fetal vertebral artery resistance index (VA RI), pulsatility index (VA PI) and peak systolic velocity (VA PSV), and describe their normal ratios to the umbilical artery (UA) throughout the second and third trimester of pregnancy. Methods: Between 19 and 41 weeks of gestation, 484 ultrasound examinations of the fetal VA and UA were performed on singleton pregnant women with uncomplicated pregnancies. The VA was examined at the anatomical point where the artery surrounds the lateral masses of the atlas between the first cervical vertebra and the occipital bone, and values were obtained for the VA RI, VA PI and VA PSV. The 10th, 50th and 90th percentiles were subsequently generated for these parameters and their ratios to the UA. Results: The VA RI and VA PI reached their maximum values at the end of the second trimester. Both indexes subsequently decreased due to an increase in the diastolic flow. Conversely, the VA PSV values increased progressively until the end of gestation. As for the VA/UA ratios, the RI and PI were higher in the middle of the third trimester and decreased slightly afterwards. On the other hand, the PSV increased progressively until the end of pregnancy. Conclusions: The fetal VA can be visualized with Doppler ultrasound as early as 19 weeks’ gestation. In this study, reference values of the VA RI, PI and PSV and their ratios to the UA during the second half of pregnancy have been provided for fetal research. However, future work is necessary to further explore the possible applications of VA Doppler examination in fetal medicine.

Doppler study of the fetal vertebral and middle cerebral arteries in fetuses with normal and increased umbilical artery resistance indices

“…The right and left VAs finally merge in a common basilar artery, which joins the MCA/ICA system at the circle of Willis. Based on our previous works, VA measurements were obtained during fetal apnea 14–16. Initially, the color Doppler window was positioned on the nuchal area with the fetal spine in an anterior position.…”

“…In previous works, we studied the VA Doppler impedance and described the VA brain sparing mechanism 14–16. In this paper we compare the VA and MCA brain sparing systems in fetuses with abnormal umbilical artery (UA) impedance.…”

Neonatal Acid-Base Status in Fetuses with Abnormal Vertebro- and Cerebro-Placental Ratios

“…Conventionally, fetal brain vascular surveillance has been performed using the MCA Doppler [24][25][26] . However, recently, an easy and standardized procedure for the VA Doppler measurement has been described [11,[27][28][29] .…”

The vertebral artery Doppler might be an alternative to the middle cerebral artery Doppler in the follow-up of the early onset growth-restricted fetus

“…The VA is consequently a much older vessel, which in humans represents 30%, in the Cheiroptera, Rodentia, or Ruminantia 50%, and in dogs 70% of the cerebral flow . However, despite all these facts, it was not until recently that an easy and standardized procedure for the VA Doppler measurement was described …”

“…From a phylogenetic point of view, VA supplies the older areas of the brain, brain stem, and cerebellum, which have been shown to present better adaptive mechanisms to hypoxia than the neocortex irrigated by the ICA and its continuation to the middle cerebral artery (MCA) . These differences, which might be partially the result of different arterial responses to hypoxemia, prompted us to initiate a research line on the fetal VA Doppler . Our aim in this work was to describe preliminary data concerning its application in the follow‐up of fetuses affected with severe growth restriction [fetal growth restriction (FGR)].…”